The present invention relates to a printer and more particularly to a printer which can also be used as a typewriter in conjunction with an external device such as a keyboard of a personal computer.
It is known that a printer which moves and stops the printing head for every one character to be printed, such as one having a daisy wheel type, is able to print immediately after each data is inputted from an external device. Therefore, such a printer can be used, for example, as a typewriter by using a keyboard of a personal computer. When the printer has a ribbon lift mechanism, the print ribbon is lifted to a printing position with each character data input from a normal lower rest position. This facilitates the operator to check the print. However, when the character data are continuously inputted, the ribbon is held at the printing position for speedier printing and for longer mechanical life. Unless subsequent printing data is supplied in a preset time interval, the ribbon returns to the rest position.
As far as a typewriter is concerned, a typewriter which has the ribbon lift mechanism and of which the operator can vary the time interval by means of a dial or keys on the keyboard has been disclosed for improvement in adjustment of the time interval according to the degree of the operator's skill in typing, for example in Japanese published unexamined patent applications Nos. 60-64884 and 60-201981. An English patent application claiming priority based on the former application is laid open on June 5, 1985 by No. 2148796A, and an EPC application based on the latter is laid open on Oct. 2, 1985 by No. 156359A.
On the other hand, there is a printer which can be used in two different ways, that is, as an external device of a computer to print out the data or text thereof and as a typewriter to print out the characters inputted from the keyboard connected thereon. In such a printer, both a data transfer rate and a pattern of interval variation between data are different between the case when the data are inputted from a memory of the computer and the case when the data are inputted from the keyboard. The data transfer rate when the data come from an external computer device or when they come from a memory is far greater than when they come from a manually operated keyboard.
Further, the difference in the patterns of the interval variation between the above-mentioned two cases is too remarkable to be disregarded. More particularly, the intervals are always the same in every occasion when the data are inputted from the memory of the computer, while the intervals differs depending on many factors when the data are inputted from the keyboard by the operator; that is, the interval between characters within a word is generally shorter than that between words, which is generally shorter than that between sentences. Therefore, it is required to vary the time interval from the time point the last character data is inputted to the time point the printing ribbon is shifted down to the rest position corresponding to a data supply source device connected to the printer mechanism.